The Behavioral Sciences Research in HIV Infection Program at Columbia University provides postdoctoral training in human sexuality research applied to HIV prevention science and is grounded in formal training in research methodology, design, and statistical analysis appropriate to the overriding goal of producing trainees capable of assuming independent research careers. The program emphasizes multidisciplinary training with matriculation in a specialized track for human sexuality research trainees within a Master of Science degree program in Biostatistics in the Columbia School of Public Health. In so doing, the applicant aims to emphasize theoretical rigor, methodological innovation, and practical application in order to provide solutions to the complicated psychological, social, and public health dilemmas posed by the HIV epidemic. The program builds on a record of 10 years of recruitment and training of postdoctoral research trainees in the behavioral determinants of HIV risk behaviors, models of behavioral change, and other vital mental and public health aspects of HIV infection. In this resubmission, the applicants refocus the training program's emphasis to provide intensive training in human sexuality research that is guided by the HIV Center for Clinical and Behavioral Studies' history of psychosexual assessment and methodological research and in the number of faculty members who are experts in this area. In the next 5 years of the training program, the applicants propose the appointments of three postdoctoral trainees each year for 3 years of support per trainee. In the first year, trainees will undertake course work in the School of Public Health, culminating in an MS degree in Biostatistics. In the second and third years of support, trainees will implement original research projects under the guidance of faculty mentors who are funded, experienced senior investigators with histories of independent funding, interdisciplinary collaboration, and mentoring predoctoral or postdoctoral trainees. Research training is further supplemented by seminars, courses, and other educational activities at the HIV Center, the Columbia School of Public Health, and the Columbia-Presbyterian Medical Center. The Program intends to continue with a balance of trainees with health professional and non-health professional backgrounds.